1. Field of the Invention
The invention relates in general to an input circuit of an integrated circuit, and more particularly to an input circuit capable of preventing current backflow.
2. Description of the Related Art
Communications between electronic products may be achieved through physical transmission lines and special communication standards. In general, an integrated circuit that provides signals may be referred to as a source integrated circuit, and an integrated circuit that receives signals through transmission lines may be referred to as a sink integrated circuit.
Differential signals are adopted by many communication standards to achieve quite high communication signal transmission speeds. However, for high-speed communications, a sink integrated circuit frequently requires a termination resistor for reducing signal reflection and increasing the transmission speed. For example, a termination resistor may be installed in a sink integrated circuit and be connected between a bonding pad and a power line. During normal signal transmission, a power line of the source integrated circuit and the power line of the sink integrated circuit jointly drive transmission lines connected.
When an electronic product including the sink integrated circuit is turned off, a power voltage of a power line of the sink integrated circuit theoretically drops to 0V as time passes. However, in practice, it is possible that the power line of the source integrated circuit feed a backflow current to the power line of the sink integrated circuit through the transmission line and the termination resistor of the sink integrated circuit, resulting in a voltage greater than 0V. Such current backflow may cause in errors in default values of the sink integrated circuit when the electronic device including the sink integrated circuit is again turned on. Therefore, there is a need for a solution that considers and prevents current backflow.